Protective device for electric current-consuming apparatus



June 30, 1925.

O. DREYER PROTECTIVE DEVICE FOR ELECTRIC CURRENT CONSUMING APPARATUS Filed April 25, 1924 Fig.3

In V01] for:

Patented June 30, 1925.

UNITED STATES OTTO DREYER, OF ESSEN-ON-THE-RUHR, GERMANY.

PROTECTIVE DEVICE FOR, ELECTRIC CURRENT-CONSUMING APPARATUS.

Application filed April 25, 1924. Serial No. 708,994.

To all whom it may concern:

Be it known that I, O'rro DREYER, a citizen of the German Republic, and residing at Essen-on-the-Ruhr, Rhenish Prussia,

Germany, have invented certain new and useful Improvements in Protective Devices for Electric Current-Consuming Apparatus, for which I have filed an application for Letters Patent in Germany, on March 3,

1923, and of which thefollowing is a speci fication.

The invention refers to a protective device for electric current consuming apparatus against excessive heating, wherein a temperature switch, when attracted, effects the switching off of the endangered apparatus. The object of the invention consists in constituting such a protective device in this manner, namely, that, after the switching oil and cooling taking place thereupon, said device automatically sets itself into the position for" use. For this purpose according to the invention, there is arranged in a magnet coil serving when required simultaneously as heating coil an armature held in its normal position and usually by means of a soldered joint or the like, the said armature being displaceably arranged in said coil in this manner, namely, that when softso ening of the soldered joint consequent on an excessive or unallowable increase of temperature occurs, the said armature is displaced in the direction of releasing the switch action owing to the electromagnetic action of the coil, but after breakage of the circuit, on the other hand, is returned to its normal position owin to gravity or spring action and is hel therein a ain owing to the cooling of the solder meta The new device may simultaneously be constructed as a maximum current switch, that is, in such manner that it functions not only in the case of excessive heating of the consuming apparatus to be protected, but

also in the case of overstepplng the allowable maximum current strength. To this end the magnet armature influenced by the coil is provided with a non-magnetic weightcore, whcrewith it is connected by means of a soldered joint. When said allowable maximum is exceeded the armature to ether with said core suspended from it is rawn into the coil, while when the maximum alscrewed on the lateral lowable temperature is exceeded the soldered joint softens and the armature freed thereby from its weight-core is drawn into the coil by a comparatively small current and so causes the switching ofi of the endan ered circuit.

T e armature and weight core are preferably slidable. telescopically the one in the other, the tubular armature loosely surrounding the weight-core being fastened at its upper end to a central rod, which is guided in a downwardly closed bore in the weight-core and soldered thereto with readily fusible metal.

The annexed drawing illustrates by way of exam le, a preferred form of a heat protecting evice simultaneously constituting a maximum current switch. In the drawing:

Fig. 1 is a longitudinal section through the rotective device in its normal position,

Flg. 2 shows the armature raised while the weight-core remains below, that is, on the unsoldering of the soldered joint,

Figs. 3 and 4 show the special form of the armature.

Within the insulating body 1, which simultaneousl constitutes heat protection, is

sitioned t e coil 2 serving as draught and eating means and traversed b the current of the apparatus to be protecte e. g. a crane motor. The coil 2 is wound on a thin metal cylinder 3 and actuates the releasing device within it. The latter consists substantially of a tubular armature 4 of magnetic material and a wei ht-core arranged therein, the latter preferab y of high specific gravity but of the minimum lpossible s ecific heat, and ma be, e. g. of cad, whic weight-core is jac eted outside with thin brass. The armature 4 at its upper portion also has a thin brass jacket 7 and is secured above the cover 8 to a metal rod 9, which is guidedin a downwardly closed bore 10 in the weightcore 5. The said bore is lined with a brass socket 11 narrowed above by an insertion 12, to whichsocket the rod 9 is soldered at its lower, thickened end 14, as also, if desired, above the insertion 12. The releasingarmature 4 with the weight-core 5, in

the normal position shown in Fig. 1, is

supported on a transverse piece 15, which is adjustable in height by mleans 8f a7 nut l116 ysittuel atte into the form of two points 20. The setting of the armature is such that the greatest part of the iron body, and indeed the lower annular part 4 is normally located quite outside the coil and only its points 20 8X.

tend into the hollow ofthe latter. By this construction, very exact setting of the am mature to a predetermined current strength is rendered possible and it is also obtained that the releasing device is employable both for direct and alternating current without the employment of a laminated iron body.

Above and opposite the releaser comprising the elements 4, 7 and 8, a metal bridge 21 is arranged, which, when the armature is attracted, is lifted by the latter and thereby the contacts 22 are inter-connected. In that way the auxiliary circuit'of an electromagnetic cut out is closed in known manner or a short-circuit is produced between the poles of the consuming apparatus, this resulting in the switching ofi' of the circuit by means of the ordinary safety fuses connected in series with the apparatus to be protected.

The mode of operation of the device is as follows In the position shown in Fig. 1, the releaser is to be regarded as an armature heavily loaded by the lead weight so long as the dangerous condition in the heating of the windings of the consuming apparatus to be protected, and therefore the unsoldering of the soldered joint has not occurred, which armature at a predetermined adjustable current strength (a multiple of the normal working current strength) is drawn into the interior of the coil 2 and owing to its jumping movement actuates the switching mechanism 21, 22 so that the endgngered consuming apparatus is switched o When the motor to be protected attains a dangerous temperature there occurs, since the coil of the releaser can have approximately the same heat constant as the motor to be protected, such a heating inside the coil 2 that the readily fusible solder softens. A substantially smaller force is now required to lift the iron armature 4 and 'with it the metal cylinder and the pin 9 connected with them above the cover 8, the lead core 5 remainirig stationary on the lower support 15. After the armature has been attracted, it falls back by gravity into its normal position.

The relationships can be so chosen that when the dangerous condition arises the armature operating without the lead weight corresponds with a current below the normal working current, but on the other hand when the armature is loaded attraction oc-. curs at higher values, e. g. at 2 to 3 times the working current. The sensitiveness of the releaser after the dangerous temperature has been reached remains the same until the temperature of the endangered motor and consequently the heat emitted by the coil has so far gone down that secure soldering at the soldered joint results. After this conditions has arisen the releaser .is again insensitive to excess current permissible for working.

The advantage of the releasing device as compared with devices heretofore resides, as is readily obvious, mainly in the simple compact mode of construction, wherein undoubted reliability is guaranteed. The employment of an additional weight of high specific gravity and simultaneously low specific heat, e. g. of lead, is specially. advantageous for the functioning of the releaser in the case of short period, high overloads which lie just below that current strength whereat the releasing device comes electromagnetically into action.

The invention is of course not limited to the example illustrated, but other embodiments thereof are possible. In particular, the magnet armature of the temperature switch might be moved back into the normal position by a spring instead of by the action of gravity. Moreover heating of the soldered joint might be effected directly by the consuming apparatus to be protected, in which case the magnet coil need not be constituted as heating coil.

Claims:

1. In a device for protecting electric circuits againstexcessive heating and overload, in combination; a temperature switch comprising a non-magnetic weight-core, a tube-like magnet armature loosely surrounding said weight core, a soldered joint normally connecting said weight core and said armature, said weight core and said armature being guided for vertical movement and being normally held in their lower most position by gravity, and a magnet-coil sur-'. rounding said armature and connected to the circuit to be protected.

2. In a device for protecting electric circuits against excessive heating; in combination, a temperature switch comprising a magnet armature guided for rectilinear movement, and a soldered joint holding said armature in its normal position, a magnet coil arranged concentrically to said armature and adapted to be connected to the circuit to be protected, said magnet coil acting simultaneously as a heating coil and being adapted to unsolder said soldered joint and, at the same time, to draw said armature into said coil, to thereby actuate said temperature switch, and weightmeans for returning said armature to its normal position.

- 3. In a device for protecting electric circuits against execessive heating, in combination, a temperature switch comprising a- "comprising a movable switch member, a tubelike magnet armature for moving said switch member, said tube-like armature being at its-upper portion provided with upwardly widened slots so as to form points on said-armature, a leaden weight-core arranged in said tube-likearmat-ure, a soldered joint normally connecting said armature and said weight-core, said armature andsaid weight-core being guided for vertical movement and being normally held in their lowermost position by gravity, a vertically adjustable support for said armature and said. weight-core, a magnet-coil arranged concentrically to said armature and connected to-the circuit to be protected, said magnet-coil bein simultaneously constructed as a heating coil having substantially the same heat constant as the circuit to be protected. 5. In a device for protecting electric circuits against excessive heating and overload, in combination: a temperature switch comprising a magnet armature, a non-magnetic weight and a soldered joint connecting said magnet armature to said non-magnetic weight, said armature and said weight being guided for vertical movement and being normally held in their lowermost position by gravity, a magnet coil surrounding said armature and connected to the circuit to be protected, said magnet coil being adapted, on the one hand, on unsoldering said soldered joint to draw said armature into said coil, and, on the other hand, on occurance of a current of excessive strength to i draw said armature and said non-magnetic weight commonly into said coil-and thereby to actuate said temperature switch.

6. In a device for protecting electric circuits against excessive heating and overload, in combination: a temperature switch comprising a non-magnetic weight-core pro-- vidcd with a central bore closed at its lower end, a tube-like magnet armature surrounding said weight-core, a rod fixed to the upper end of said armature and guided in said bore of said weight-core, a soldered cult to be joint normally connecting said rod to said weight-core, said weight-core and said armature being guided for vertical movement and being normally held in their lowermost position by gravity, a magnet-coil surrounding sald armature and connected to the cirrotected.

7. In a evice for protecting electric circuits against excessive heating, in combination:' a temperature switch comprising a tube-like magnet armature and a soldered joint holding said armature in its normal position, and a magnet coil arranged. concentrically to said armature and connected to the circuit to be protected, said tube-like armature being at its upper portion provided with upwardly widening slots so as to form points pro'ecting into said magnet-coil.

8. In a evice for protecting electric circuits against excessive heating, in combination: a temperature switch comprising a tube-like armature guided for longitudinal movement, an adjustable abutment for said armature, a soldered joint for holding said armature in its normal position, and a mag-v net coil arranged concentrically to said armature and connected to the circuit to be protected, said tube-like armature being at its upper portion provided with upwardly widening slots so as to form points on said armature which project into said magnet e01 9. In a device for protecting electric circuits against excessive heating and overload, in combination: a temperature switch comprising a non-magnetic weight-core, a tube-like magnet armature loosely surrounding said weight-core, a soldered joint normally connecting said weight-core and said armature, said Weight-core and said armature being guided for vertical movement and being normally held in their lowermost position by gravity, a vertically adjustable support for said weight-core and said armature, a magnet coil arranged concentrically to said armature and connected to the circuit to be protected, said tube-like armature being at its upper portion provided with upwardl widening slots so as to form points on said armature which project mto said magnet coil.

10. In a device for'protecting electric circuits against excessive heating 'and overload, in combination: a temperature switch comprising a non-magnetic weight-core, a

tube-like magnet armature looseliy surround-. mg said weight-core, a soldcrc olnt northe lower portion of said weight-core and said armature, a supporting bar for said weight-core and said armature, said supporting bar being guided in the slots of said threaded tube, and a nut screwed on said tube for vertically adjusting said supporting bar, a magnet coil arranged concentrically with said armature and said weight-core and connected to the circuit to be protected, said tube-like armature being at its upper portion provided with upwardly widening slots so as to form points on said armature which 10 project into said magnet coil.

In testimony whereof I affix my signature.

OTTO DREYER. 

